The long range goal of this project is to combine immunocytochemical methods with light and electron microscopy to study cellular mechanisms of myelin formation, breakdown and regeneration. Nervous tissues from experimental animals and patients with demyelinating diseases have been studied in the following current projects: 1) Distribution of myelin-associated glycoprotein (MAG) and basic protein in acute stages of CNS Wallerian degeneration 2) Distribution of MAG and proteins in compact peripheral myelin (Po, P1, and P2) in lesions of idiopathic polyneuritis 3) Localization of Po myelin protein in Schwann cells and myelin during PNS myelination.